Safe to run Pro Mini 16mhz at 3.6V?

I know that the official datasheet for the 328 says that the minimum voltage for 16mhz is 3.84V or something like that, but I was wondering if it would be safe to run just a little lower. Going down to 3.6V would make my project use fewer parts and work much better, and I know the arduino will run like that

...I just don't know how long it will run. AFAIK, the chip is rated at about 10 years of running 24-7; my goal is to run this project for 5 years, also 24-7. Am I going to have problems down the line?

Why would anyone recommend or guess if you could run correctly for 5 years @ 24/7 by ignoring the Atmel specifications? So many variable can happen over five years, temperature variations, electrical noise margins can change, etc, etc.

It's like the movie, "do you feel lucky, punk?" ;)


Actually, it was that guy's lucky day; he just didn't take the chance (Clint Eastwood was out of bullets).

The reason I guessed that it might be possible is because I have run computer processors under voltage and over clock for 5 years without issue.

This isn't a huge overclock either...I'm only dropping the spec voltage for 16mhz by .24V (I have seen larger drops from USB cables). Part of me thinks that I could get away with it just be using high quality connectors...but I might be wrong.

Part of me thinks that I could get away with it just be using high quality connectors...but I might be wrong.

That's the point. Either you play it by the book and try to be safe you're willing to take a risk. Another question, why don't you use the 3.3V Arduino pro mini with 8MHz? Is clock speed really so critical for your application?


but I might be wrong.

And that is why you posted the question. My point is would you take anyones word over the datasheet specifications as the deal maker? You seem to understand the basic issue well, but still you seek validation from users?

My opinion: If I was using such a system for my own use I would most likely try it and see if it worked and if it did let it try and run for 5 years. However if I was selling or giving a solution for someone else I would not without disclosing the risk and asking them to accept it at their own risk. Full disclosure so to speak. ;)


Thank you, that is what I wanted to know. I'll take the risk since it is for me ($19 plus shipping isn't terribly high stakes). If it burns out before the 328 is ancient history, I'll post back.

BTW...this does need 16mhz...only about 0.001% of the time, but it does need it.

only about 0.001% of the time

That means for 864 ms per day or for 5:15 per year for a total of less than 1/2 hour until 2016. Usually, you have other error sources more problematic than this.


Running at a lower voltage than the spec is always safe. But whether or not it is stable is another story.

I have done a few projects with 3.3V/16Mhz setup and haven’t had any issues at all.

If you do the math on Figure 28-1 of the data sheet, I believe it shows you need 6/10 of (4.5v-2.7v)+2.7v = 3.78V to be on the line for safe operation at 16 MHz. Why not add a boost regulator & get your voltage up a little? The things are little, just 3 pins on 0.1" spacing, stand it up vertically & I don't think it takes any more room than a TO-220 package 7805. other models also available that can do a higher current also.